noetzli



Aug. 21, 1928.

F. A. NOETZLI DAM Filed July 13, 1926 A IO INVENTOR Patented Aug. 21, 1928.

ll lTE. STATES FRED A. NOETZLI, 0]? 110$ ANGIELES, CALIFORNIA.

DAM.

Application filed. July 13,

This invention relates to the construction of concrete and masonry dams, and the primary object of the invention is to provide a dam of this type which will. be less expensive and which can be built in a shorter period of time than. dams such as heretofore constructed.

Most concrete'and masonry dams as heretofore constructed have been of the gravity, arch, multiple arch or deck slab type. Some of these dams depend for stability upon the weight of the structure alone, such as gravity dams. (lthers, like arch and multiple arch dams, depend upon arch action, and in deck slab dams the water pressure is supported by slab or beam action.

In both multiple arch and deck slab dams the water pressure is transn'iitted by means of arches or deck slabs upon buttresses. This transmission of stresses involves arch action or bending moments which may introduce large stresses in the deck and necessitates, in some cases, the use of reinforcing, steel for taking care of tension stresses. The decks of these dams are usually thin and are subject to deterioration from frost action.

The objects of my invention are, first, to build a dam which in principle is a gravity dam and in which the parts of the dam in contact with the water in the reservoir are not subject to arch stresses or lateral bending moments and corresponding stresses; second, to build such a dam of a combination of buttress walls and enlarged buttress heads by means of which the water pressure is. supported by compression and shear stresses without involving arch action or bending moments in a direction substantially perpendicular to the buttress; third, to build a dam composed of buttresses of the type described which are substantially independent of each other but which form a. continuous surface towards the water side from one side of the canyon to the other; fourth, to build a dam for which the sliding, factor in horizontal planes is closely regulated by a definite inclination of the rip-stream face of the dam.

In the accompanying drawing in which my improved dam is illustrated, Figure l is a typical side elevation of a buttress;

Figure 2 is a typical horizontal section through two adjacent buttresses;

Figure 3 is a typical section tlirough the buttress head illustrating the manner in which the pressure or the water in the resist 1926. Serial No. 122,141.

voir is transmitted by means of the buttress head to the buttress wall;

Figure 4: is a typical section thrciilgh the buttress head a short distance above the foundation;

Figure 5 is a typical section of the buttress head near the crest of the dam where the Water pressure is relatively small.

Referring to Figure 1: The dam shown compr'ses buttresses B, said buttresses having an enlarged buttress head 6 towards the water side of the buttress wall '7. The buttresses are supported by the foundation material 8. The rip-stream face 9 of my improved dam preferably has a variable slope similarly as shown on Figure 1. The slope at the various elevations of the dam may be determined mathematically in the following manner and will result in a relative minimum of concrete being; involved in a dam of this type.

Current practice of dam design requires that the sliding factor in horizontal planes at any elevation of the dam must not exceed a certain permissible value of, say, 0.75. The sliding factor f of a dam is equal to the horizontal water pressure H divided by the sum of the weights of the dam D and of the water V overlying the clam.

This relation is expressed by the formula The larger the sliding factor is for values of 7 less than 1.0, the less concrete in general Sliding factor f:

there will be in a dam of the character described inthis specification. However, pres ent practice limits the sliding factor to a value of f= 0.75. Either by an analytical method, or by cut and trial, I determine the up-stream slope of my dam so that the sliding factor is as close to the value of f=0.75 as practicable. For certain foundation conditions, asliding factor of f=O.65 may be all that is permissible while for very good foundation rock a value of f=0.80 or more,

may be practicable. For each sliding factor malts the sliding factur of in;

than 0.75. Act the lower elevations the upstream face is preferably inclined just a sufficient amount to add enough ater load to the weight of the dam above the horizontal section investigated to give the sliding factor the desired value.

For a permissible sliding factor of 0.75 and for a span 1 00 ft. on thewater side of the buttress head 0, the rip-stream slope of my dam may be practically vertical in the upper 50 ft. of the dam. One hundred feet or more below the crest the slope may, be approximately 6 horizontal to 10 vertical. For a. sn'ialler sliding factor. the lip-stream slope will be flatter, for a larger sliding factor it will be steeper. For different spans 1 of the buttress head 0. the up-stream slope of the dam will also be different from the above one but afairly definite law will hold for each value of the span 1 and a corresponding size of the buttress head.

There will be stitleners 10 and an abutment Wall 11, if necessary, for each buttress wall to provide for safe column action and to prevent the buttress wal ls from buckling. The thickness of the buttress walls may be detern'iined in sucha manner that the pressure of the water, which pressure is transmitted through the buttress head upon the buttress wall, cor responds approximately to the maximum permissible unit compression stress in the concrete of the dam. In general, this pressure is between 4.00 and 500 lbs. per square inch. The length of the buttress andthe corresponding down-stream slope ofthe same are then determined according to well-known methods of statics. At the upper elevations of the dam the buttress walls are given a practical minimum thickness regardless of the value of the water pressure.

The buttress head 6 has a substantially constant length ta-long the face of the damn As the buttress wall 7 is ordinarily thicker at lower than at-upper eleva-tionsof the dam, the buttress head 0 extends laterally a lesser amount beyondthe buttresswall 7 at lower than at upper elevations ofthe dam.

In case that itis desiredto spill the surplus Waters in the reservoir direct-ly over the dam, a clown-stream slab 12 of reinforced concrete is provided between thebuttress walls 7. The slab 12 may be of sulficient thickness and strength to support bet-ween the-buttresses its own weight and the weight of the water overflowing the dam. ()therwis'e, it may be supported by beams 13 resting on the buttress walls 7 or theabutment walls 11.

Fig. 2 shows a horizontal section through the dam along-the line 2-2 of Fig.1; The buttress head 0 is shown curved toward the water side with: a radius-R; The central an 'le wet the arc of the buttress head 6 gives asafeandvery economical shape of the buttress head for values of re lying between. 00 and 90. The angle 50 should be about 90 for relatively low dams and may be nearer 00 for relatively high dams. The butt res-i head may also be rounded as shown at N of Fig. 2. The average angle :13, also in this case is preterably substantially between the values of 00 and 90 both from the point of view of economy and safety. At the junction between two buttress units there may be additional con crete material lit cast integrally with the but tressliead 6 for the purpose ol providing a greater thickness of concrete against the water and thus increase the impermeubilily of the dam. ln general, the cross section of the concrete material 149 is larger at lower ole vations than at upper elevations of a dam. There is no direct struc! ural connection on the water side between two adjacent buttresses. The junction between two buttresses serves as an expansionjoint J. In order to make this joint watertight", l provide a. flexible copper water stop 20 or other suitable means for preventing the water in the reservoir from escaping! through the joint J.

There may be'draiuage holes 15 in the buttress heads 0 for carrying ol'i seepage water. In case of a practicallyimpervious bmlrocl; and :1 first class quality of concrete these drainage holes may be omitted. in order to increase the stillness of the luntrcss walls T they may comprise two separate walls '7' which are braced by cross walls 10 between walls 7 for stiffeningpurposes Referring now to Fig. 3, a typical rcction through the buttress head 0 shown along the line 3-3 of Fig. l. The arrows .2 indi cate the direction of the water pressure upon the curved surface ot the blittlcss head (3. 'llhe arrows point to the center (ll of l'lll' arc of the curved face of the buttress hca d (i. and the water pressure upon the individual elo ments (a of the arch' is t-l;.li."llllil(fll by direct radial compression in the direction o t' C upon the buttress wall 7. The lip-stream face of the buttress head 0i. symmetrical to the center line C l of the buttress wall 7 'There are therefore no bern'ling moments or arch stresses produced in thebuttress head 0. thus giving a direct and therefore statically well determined transmission of the water prawsure upon the butt .4 wall 7. All uuceu tainties as to arch or bending: stre ses are thus eliminated;

Referring now to Fig. 4:, a typical section through the buttress head 0 is shown uloiu l the line tl of Fig. 1 a short distance above the foundation of thedam. The concrete of the buttress head will shrink :l'tcr pouring: and expand or contract under the inlluence of Water soaking or drying out and on account of changesot the temperature: lf the span 1 is considerable, vertical cracks 0 might occur in the buttress heads and ein luuger the safety of the structure. If the span 1 more than 50 or 00 feet, I provide sliding and ex. pansion areas 17 on one or both sides of the hut-tress heads 6 preferably a short distance above the foundation, such as shown in Fin. 4. The areas 17 may lie either in approximately horizontal planes, or perpendicularly to the upstream slope of the dam, if desired. The areas '17 are coated with asphaltum or other suitable material to prevent bonding of the concrete and to facilitate the minute movements due to the expansion and contraction of the concrete of the buttress head 6 in the direction of the span 1. The lensgth 1 is determined in such a way that the length 1 of the contiguous portion of the buttress head 6 is not more than or feet, and preferably less. Experience has shown that a body of concrete of less than 50 feet length is much less liable to produce shrinkage cracks 6 than a body of concrete of greater length.

Referring now to Fig. 5, a typical section through the buttress head 6 is shown along the line 55 of Fig. 1. For some distance below the crest of the dam the water pressure is relatively small and the quantity of concrete in the buttress head 6 with a circular u p-stream face is relatively too large for an economical transmittal of the water pressure to the buttress wall 7. Some economy may be effected by making the up-stream face of the buttress head 6 three-centered or straight, as shown in Fig. 5. In any case the shape of the buttress head 6 should preferably be such that the lines of pressure on areas a; of the buttress head 6, which are symmetrical to the center line C -C of Fig. 5, intersect in points P which lie on the center line- (h -(l of the buttress wall 7.

In constructing my improved dam I build buttress heads 6 of curved contour integrally with buttress walls 7 in more or less continuous horizontal layers from the foundation up. I provide an open expansion joint J between each two adjacent buttresses and make this joint water-tight by suitable means. On a rock foundation. with fissures I provide drain holes 15 from the rock up through the buttress heads 6. The upstream slope of the dam may be irregular, for instance, as shown in Fig. 1. Otherwise it may be straight.

I claim:

1. A dam comprising a buttress wall and a buttress head supporting the water pressure certain portions of said buttress head extending laterally on both sides of said buttress wall, said buttress head having such a corn tour on the water side that .said water pressure is transmitted by said buttress head upon said buttress wall by direct compression.

2. A dam comprising a buttress head and a buttress wall said buttress head having an upstream face of curved contour, a horizontal plane through said buttress head intersecting said upstream face on a curve of substantially circular shape, the center of said curve lying substantially on the center line of said buttress wall.

3. A dam comprising a buttress wall and an enlarged buttress head, said buttress head having an tip-stream face of curved contour, a horizontal. plane through said buttress head intersecting said up-streain face on a curve of substantially elliptical shape.

4. A dam comprising a buttress wall and a buttress head, said buttress head comprising an up-stream face of curved contour, certain parts of said face extending laterally on both sides of said buttress wall, and a drainage well in said buttress head.

5. In a dam the combination of a buttress wall with a buttress head having a face of curved contour, said buttress head comprising concrete material added to the same on the sides and near the up-stream side of said buttress head, whereby the thickness of certain parts of said buttress head is increased near said up-stream side.

6. In a dam the combination of a buttress wall with a buttress head having an rip-stream face of curved contour, certain parts of said buttress head projecting sideways beyond said buttress wall.

7. In a dam the combination of a buttress wall with a buttress head having an upstream face of curved contour, the shape of said upstream fa-ce being such that the water pressure acting upon the tip-stream face of said buttress head is transmitted to said buttress wall without involving arch action and lateral bending moments in said buttress head.

8. In a concrete dam the combination of a buttress wall and a buttress head, certain parts of said buttress head extending laterally beyond said buttress wall, with an upstream face of said but-tress headof such shape that the water pressure is transmitted by said buttress head onto said buttress wall in such a manner that no bending moments and arch stresses are produced in a lateral direction in said parts of said buttress head extending laterally beyond said buttress wall.

9. In a dam the combination of buttress walls and buttress heads having an up-stream slope, said tip-stream slope being substantially vertical in the upper portions of said dam, and in said lower portions being substantially within the limits of five horizontal to ten vertical, and of seven horizontal to ten vertical, said buttress heads having such a contour on the water side that the pressure of the water in the reservoir is transmitted by said buttress heads upon said buttress walls by direct compression and without involving arch action or bending in a lateral direction.

10. In a dam comprising a plurality of buttresses, the combination of buttress walls and buttress heads having an Lip-stream face of curved contour, certain parts of said buttress heads at any elevation projecting laterally beyond corresponding parts of said but tress walls at the same elevation, said parts of said buttress heads at lower elevations of said buttresses projecting laterally a smaller amount beyond said buttress walls than corresponding parts of said buttress head at upper elevations.

11. In a dam comprising two adjoining buttresses, the combination of buttress walls with buttress heads having; an up-stream face of curved contour, said buttress heads of said adjoining two buttresses having a substantiially vertical area of substantially loose contact, said area of contact forming a joint substantially midways between said two adj acent buttresses.

12. In a dam comprising two adjoining buttresses, the combination of buttress walls with buttress heads having an upstream face of horizontally curved contour. a vertical joint between said buttress heads being located substantially midways between said buttress walls, and means for making said joint water tight.

13. A dam comprising a plurality of butt'resses, said buttresses havingbuttress heads of a contour curved in a horizontal direction, said buttress heads being joined loosely substantially midways between said buttresses, the Lip-stream faces of said buttress heads forming one contiguous surtace toward the water side of said dam.

14. In a dam the combination of a plural ity of buttresses comprising buttress heads having an up-stream face of curved contour, certain parts of said buttress heads projecting sideways beyond said buttress walls, said buttress walls having abutn'ient walls near the down-stream enrls,n11d a slab extending between the abutment alls of two adjoining buttresses ilor facilitatingot the spilling ot the surplus waters in the reservoir over the dam.

15. In a concrete dam the combination of a plurality of buttresses con'lprising :uljacent buttress heads having a itace curred in a hori- ZOIltfil.(lllQCtl(lIl and having;- an area o'l': contact between two adjacent buttress heads, with concrete material added to said buttress heads for the pur iiose of increasing the area of contact between said buttress heads.

16. A dam comprising a buttress wall and buttress head certain parts o't which are projecting laterally beyond said buttress wall, a joint in the parts oi said buttress head projecting beyond said buttress wall. and suitable .n'iaterial in said joint 'l'or preventing bonding of the concrete in the joint and for facilitating lateral expansion and contraction of said buttress head.

17. it dam con'iprising a buttress wall and a buttress head certain parts of said buttress head projecting laterally beyond said buttress wall, a joint in said parts of the buttress head tending to decrease the length or" the solid portion or" said buttress head near said joint to not more than 50 to (30 feet measured in a direction perpendicular to said buttress wall.

FRED A. NOEIZLI. 

